Groundwater monitoring is required under Federal, State, and local environmental regulations. In order to comply with these regulations, it is necessary to install monitoring wells in the vicinity of regulated facilities. The design and construction of monitoring wells and the attendant sampling equipment is sufficiently different from the equipment required for water supply wells that a new technology has been developed for the monitoring industry.
Two fundamental requirements for monitoring well construction are to construct a well that does not add to the potential pollution problem and to construct a well that can give a representative sample of the groundwater. The monitoring well industry has met these requirements by developing specialized drilling equipment and techniques. Chemists have developed techniques that are on the cutting edge of technology to analyze groundwater samples. Sample analyses in the parts per billion range are commonplace.
The equipment and materials used to sample groundwater require corresponding changes so that they are complementary to drilling and chemical analyses. Specific concerns for sampling equipment include sampling devices formed of materials that will not interact with the chemical constituents that are being analyzed; pumps which do not "strip" volatile components from the groundwater as it is pumped from the ground; sampling equipment that allows for rapid, repetitive sampling without undue cost or labor; and equipment so designed that a wide variety of hydrologic tests can be performed using the same well.
To meet the requirements imposed by exacting chemistry analyses and to minimize the costs of sample and hydrologic data collection, a monitoring well sampling system should:
Minimize the potential for cross contamination between wells by allowing installation of dedicated pumps in individual wells at reasonable expense. PA1 Be of such diameter that allows its installation in less expensive small-diameter wells. Be made of long-lasting, non-reactive materials. PA1 Allow accurate measurement of groundwater elevations. Allow for rapid removal of groundwater during well development and flushing prior to sampling. PA1 Allow for collection of non-aerated samples. Provide a ready means of monitoring the amount of water removed from the well during flushing and sample collection. PA1 Provide a ready means of monitoring water quality parameters (pH, temperature, and specific conductance) in the field. Be readily portable and lightweight for carrying to remote locations in the field.